The present invention relates to a digital switch used in a node of a circuit-switched communication network.
In future the switching function of a telecommunication network will be increasingly distributed, i.e. decentralized. Presumably data communication and telephony will also be mixed. In two new industry standards (DQDB and FDDI-II) datacom and telephony are mixed in a distributed system architecture. As regards telephony this means that also the circuit switch will be distributed.
One of the advantages with a distributed circuit connected switch is that it most often will be relatively small in each node and that the manufacturing costs for the complete switch will be proportional to the number of nodes.
A conventional time switch includes a control memory, a switch memory and a time slot counter. In the switch memory data is cyclically entered into the memory on an address which is pointed to by the time slot counter. At reading out data from the switch memory the value of the time slot counter is translated in the control memory before becoming an address to the switch memory. The data is read out in an order determined by the control memory. A processor writes into the control memory for updating a table of read out order located therein.
A distributed switch of the kind defined above by way of introduction is e.g. known from the Swedish patent application 9103719-2 which corresponds to commonly assigned U.S. patent application Ser. No. 07/990,646. A switch of this type has the disadvantage that it implies a significant increase of costs in the network.